I'll sticky this topic. Lots of good info here.
FYI, you can own a Cafepress shop for free but the free shops limit you to one design per object per shop. So you can only have one mug, one mouse pad, one hoodie, etc. If you get a paid shop you can have unlimited items and customize your store front. The paid shops are like ~$60 a year.
Don't count on getting sales from people just randomly finding your stuff on cafepress. you need to advertise outside of that. Even if you have a big site to advertise on, you still may not get many sales depending on your product prices. CP has a rather high base price which is what sucks about it. But the nice thing is that you don't have to invest in inventory or handle any of the sales transactions.